Abstract
Security is considered a critical issue in the deployment of 5G networks because of the vulnerability of information that can be intercepted by eavesdroppers in wireless transmission environments. Thus, physical layer security has emerged as an alternative for the secure enabling of 5G technologies and for tackling this security issue. In this paper, we study the secrecy energy efficiency (SEE) in a downlink underlying cognitive radio (CR)—non-orthogonal multiple access (NOMA) system with a cooperative relay. The system has an energy-harvesting (EH) user and an eavesdropper, where the transmitter provides direct communication with a close secondary user and a distant secondary user via the relay. Our objective is to maximize the SEE of the CR-NOMA system under the constraints of a minimum information rate for the secondary users, a minimum amount of energy harvested by the EH user, and maximum power availability at the transmitter and the relay that still prevents them from causing unacceptable interference with the primary user. The proposed solution to maximize the SEE is based on the low-computational—complexity particle swarm optimization (PSO) algorithm. For validation purposes, we compare the optimization outcomes obtained by the PSO algorithm with the optimal exhaustive search method. Furthermore, we compare the performance of our proposed CR-NOMA scheme with the conventional orthogonal multiple access (OMA) scheme.
Highlights
The rapid expansion of wireless networks has produced a massive increment in data traffic.The fundamental requirements for future networks such as 5G include massive connectivity of users and the Internet of Things (IoT), low latency, high energy efficiency, and higher data rates.Non-orthogonal multiple access (NOMA) has attracted extensive attention in the literature because it can provide superior energy efficiency, higher data rates, and low transmission latency [1,2]
Since we focus on enhancing the Physical layer security (PLS), we propose maximizing the secrecy energy efficiency (SEE) of the cognitive radio (CR)-non-orthogonal multiple access (NOMA) system with cooperative relaying and an EH user to prevent eavesdropper wiretaps by satisfying the following quality of service (QoS) requirements: minimum required energy at the EH user, a minimum data rate for secondary users, the maximum permissible transmission power at the relay, and a transmitter that avoids interference with the primary user
Simulation results show that our proposed scheme based on NOMA outperforms the OMA scheme, where an improvement in the SEE of around 40% to more than 100% is achieved by NOMA compared with OMA
Summary
The rapid expansion of wireless networks has produced a massive increment in data traffic. Zhang et al [6] considered a single-input single-output NOMA system with a passive eavesdropper, where the objective was to maximize the secrecy sum rate (SSR) under the constraint of minimum data rate at the users The authors compared their proposed solution with the orthogonal multiple access (OMA) method, obtaining a significant improvement of the SRR by using NOMA. Since we focus on enhancing the PLS (and to enable sustainable 5G networks), we propose maximizing the SEE of the CR-NOMA system with cooperative relaying and an EH user to prevent eavesdropper wiretaps by satisfying the following QoS requirements: minimum required energy at the EH user, a minimum data rate for secondary users, the maximum permissible transmission power at the relay, and a transmitter that avoids interference with the primary user.
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